In a lithography process to manufacture electronic devices (micro-devices) such as a liquid crystal display device or a semiconductor device (such as an integrated circuit), an exposure apparatus is used, which, by exposing a photosensitive glass plate or a wafer (hereinafter collectively called a “substrate”) to an illumination light (an energy beam) via a projection optical system (a lens), transfers a predetermined pattern that a mask (photo mask) or a reticle (hereinafter collectively called a “mask”) has onto the substrate.
As an exposure apparatus of this kind, since position control of the substrate with respect to the projection optical system has to be performed with high precision, an apparatus is known that uses an encoder system as a position measurement system of the substrate (for example, refer to PTL 1).
Here, in the case of obtaining position information on the substrate using an optical interferometer system, since the optical path of the laser to the bar mirror becomes long, influence of air fluctuation cannot be ignored.